Why a swale can be useful in your garden

Previously we have already talked about swales, the contour ditches that serve as retention basins and that collect excess water accumulated following heavy precipitation or snow melting. These are ditches characterised by the downstream embankment not compacted and on which plants, trees and shrubs are planted.

Let’s discover what their advantages are even on a small scale.

Swales mitigate rainwater run-off.

Rainwater run-off is one of the major problems in most cities. Water is seen as a danger, for the risk of flooding for example, therefore modern thinking is to get rid of it as quickly as possible. This has led to a violation of environmental management whenever heavy rains occur and we discharge raw sewage into watercourses or directly into the sea because the sewage system combines rainwater with black water discharges in these emergency situations. Usually we think of rainwater runoff as a problem that can only be addressed and solved by governments, institutions or experts. In reality there would be no “problem” if citizens did their part.

“Despite the world’s problems being increasingly complex, the solutions remain so simple as to be almost embarrassing” – Bill Mollison, father of permaculture and author of “Introduction to Permaculture” and the book “Permaculture: A Designers’ Manual”.
Swales are a less demanding solution for collecting rainwater than cisterns.

Collecting rainwater in cisterns or barrels means having to purchase a lot of different components. Gutters’ downpipes need to be connected to the collection container (and if necessary connect together more than one container) and then channel the excess flow towards sewage drains or towards other destinations. One also needs to be able to clean the barrel frequently, add anti-mosquito products and insert a tap to fill the watering can or connect a hose to water. Moreover all these components deteriorate over time with sun and weather, so they need to be repaired or replaced. Finally the water pressure in the barrel is very low and, honestly, using it is a nuisance. Believe me, managing to water without water pressure really means taking forever! One can try to connect a solar-powered pump, but the results aren’t exciting. Think about how much engineering and the costs for purchasing components, when one could simply dig a pit in the ground and let nature slow down water runoff, distribute it and store it for us. Really very simple (after having dug the pit obviously!)

Another problem, if one owns water collection containers, is that one needs to establish how to deal with moments when it’s in excess. Water has great potential and it would be irresponsible, as well as wasteful, to channel litres of water towards nowhere in particular. This is one of the reasons why local institutions don’t actively encourage water collection: one person who floods the neighbour’s cellar or who creates a mosquito pond is enough to put this good practice in a bad light. So let’s collect water in the ground responsibly and use it to our advantage!
Swales are more efficient than cisterns.

Healthy soil needs water. Organic matter functions like a sponge, retaining several times its weight in water without difficulty. Toby Hemenway in his book “Gaia’s Garden” explains to us that three quarters of dry soil can easily retain a quarter of water. When we transfer this concept to our garden we realise that if it were covered by 30 cm of fertile and moist soil it would retain as much water as a pond 8 cm deep and the size of the garden itself. At the same time it would be prohibitive economically to install a cistern that can contain such a quantity of water, but the soil retains it for us and even for free!

Here are a couple of actions that can maximise the benefits of a swale minimising evaporation and the time to dedicate to the garden:
- regularly add organic matter (compost and mulch) to the swale embankments;
- shelter the swale embankments from the sun by planting dense vegetation.
Swales create self-sufficient ecosystems.

Swales collect water and distribute it in the soil where it’s needed. Instead of draining water away or letting it stagnate on the ground, swales channel it towards an underground reservoir. Nature has its irrigation system built in: when water is needed it’s released naturally without the need for further interventions after the construction of the swale. This underground reservoir attracts numerous microorganisms that begin to eat, release nutrients into the soil, reproduce and… voilà, we find ourselves generating organic matter and fertilising precisely where we needed it. This means less maintenance, which saves us time and money. The more organic matter forms the more it keeps the soil moist. With a greater quantity of organic matter the system can resist better both heavy rains and drought periods. The more the water reservoir grows and nutrients in the soil increase, the simpler gardening will become.